Hello All, In the world of astronomy we currently have comet Lulin which will be observable in binoculars and telescopes for another couple of months. So I set up my scope to take a picture of it. So the DSP part comes in two ways. First since the Earth rotates you need to have your scope track the stars to counter the rotation. Even with a moderate quality "clock drive" on a scope, the tracking is not generally great and when you try to track for a minute or more errors (periodic and misalignment) in the clock drive will show up. So the fix these days is to piggyback a smaller scope onto the main scope and put a ccd camera on the "guide scope." The ccd camera is connected to a laptop via usb and the camera is read into the computer every few seconds. You select a star that the camera sees to use as a guide star and the computer tracks the errors in the measured star position when compared to the ideal and these errors are then Kalman filtered and the corrections are sent to the telescope's mount to keep the guide star centered up. Another DSP aspect (a pretty simple one yet effective) is taking multiple short exposures (1 to 10 minutes each) and stacking them together to average out the noise. You may also shoot a dark frame and use that to flatten out thermal noise in the sensor. This often shows up lighter portions along the edge or corner of the sensor. Here is a result: Comments welcome. http://www.claysturner.com/CometLulin.jpg I hope you all enjoyed.
Slightly OT: Comet Lulin and Kalman Filtering and signal averaging
Started by ●February 25, 2009
Reply by ●February 25, 20092009-02-25
clay@claysturner.com wrote:> Hello All, > > In the world of astronomy we currently have comet Lulin which will be > observable in binoculars and telescopes for another couple of months. > So I set up my scope to take a picture of it. So the DSP part comes in > two ways. > > First since the Earth rotates you need to have your scope track the > stars to counter the rotation. Even with a moderate quality "clock > drive" on a scope, the tracking is not generally great and when you > try to track for a minute or more errors (periodic and misalignment) > in the clock drive will show up. So the fix these days is to piggyback > a smaller scope onto the main scope and put a ccd camera on the "guide > scope." The ccd camera is connected to a laptop via usb and the camera > is read into the computer every few seconds. You select a star that > the camera sees to use as a guide star and the computer tracks the > errors in the measured star position when compared to the ideal and > these errors are then Kalman filtered and the corrections are sent to > the telescope's mount to keep the guide star centered up. > > Another DSP aspect (a pretty simple one yet effective) is taking > multiple short exposures (1 to 10 minutes each) and stacking them > together to average out the noise. You may also shoot a dark frame and > use that to flatten out thermal noise in the sensor. This often shows > up lighter portions along the edge or corner of the sensor. > > Here is a result: Comments welcome. > > http://www.claysturner.com/CometLulin.jpg > > I hope you all enjoyed.Outstanding! Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●February 25, 20092009-02-25
On Feb 25, 10:54�am, c...@claysturner.com wrote:> Hello All, > > In the world of astronomy we currently have comet Lulin which will be > observable in binoculars and telescopes for another couple of months. > So I set up my scope to take a picture of it. So the DSP part comes in > two ways. > > First since the Earth rotates you need to have your scope track the > stars to counter the rotation. Even with a moderate quality "clock > drive" on a scope, the tracking is not generally great and when you > try to track for a minute or more errors (periodic and misalignment) > in the clock drive will show up. So the fix these days is to piggyback > a smaller scope onto the main scope and put a ccd camera on the "guide > scope." The ccd camera is connected to a laptop via usb and the camera > is read into the computer every few seconds. You select a star that > the camera sees to use as a guide star and the computer tracks the > errors in the measured star position when compared to the ideal and > these errors are then Kalman filtered and the corrections are sent to > the telescope's mount to keep the guide star centered up. > > Another DSP aspect (a pretty simple one yet effective) is taking > multiple short exposures (1 to 10 minutes each) and stacking them > together to average out the noise.do you cross correlate each exposure to line it up before stacking?
Reply by ●February 25, 20092009-02-25
clay@claysturner.com wrote:> Hello All, > > In the world of astronomy we currently have comet Lulin which will be > observable in binoculars and telescopes for another couple of months. > So I set up my scope to take a picture of it. So the DSP part comes in > two ways. >> Here is a result: Comments welcome. >> >> http://www.claysturner.com/CometLulin.jpg[...] http://www.space.com/php/multimedia/downloads/wallpapers/ VLV
Reply by ●February 25, 20092009-02-25
On Feb 25, 12:05�pm, "bungalow_st...@yahoo.com" <bungalow_st...@yahoo.com> wrote:> On Feb 25, 10:54�am, c...@claysturner.com wrote: > > > > > > > Hello All, > > > In the world of astronomy we currently have comet Lulin which will be > > observable in binoculars and telescopes for another couple of months. > > So I set up my scope to take a picture of it. So the DSP part comes in > > two ways. > > > First since the Earth rotates you need to have your scope track the > > stars to counter the rotation. Even with a moderate quality "clock > > drive" on a scope, the tracking is not generally great and when you > > try to track for a minute or more errors (periodic and misalignment) > > in the clock drive will show up. So the fix these days is to piggyback > > a smaller scope onto the main scope and put a ccd camera on the "guide > > scope." The ccd camera is connected to a laptop via usb and the camera > > is read into the computer every few seconds. You select a star that > > the camera sees to use as a guide star and the computer tracks the > > errors in the measured star position when compared to the ideal and > > these errors are then Kalman filtered and the corrections are sent to > > the telescope's mount to keep the guide star centered up. > > > Another DSP aspect (a pretty simple one yet effective) is taking > > multiple short exposures (1 to 10 minutes each) and stacking them > > together to average out the noise. > > do you cross correlate each exposure to line it up before stacking?- Hide quoted text - > > - Show quoted text -I did this one manually, but I do have a program for aligning and rotating each image. It needs some improvement. Rotation of each image is needed if your telescope does not use a polar (equitorial mount). I do have such a mount so translation will suffice for me. For people using alt-azimuth mounts even if they keep a star in the field perfectly aligned from image to image, the field will rotate about that star. If you combined exposures add up to minutes or more this will become apparent. I'm working on an auto align program to speed up this process. It is not unusual for one to combine a hundred images! I'm still new at this so I haven't done one with more than 10 images yet. Clay
Reply by ●February 25, 20092009-02-25
On Feb 25, 12:05�pm, "bungalow_st...@yahoo.com" <bungalow_st...@yahoo.com> wrote:> On Feb 25, 10:54�am, c...@claysturner.com wrote: > > > > > > > Hello All, > > > In the world of astronomy we currently have comet Lulin which will be > > observable in binoculars and telescopes for another couple of months. > > So I set up my scope to take a picture of it. So the DSP part comes in > > two ways. > > > First since the Earth rotates you need to have your scope track the > > stars to counter the rotation. Even with a moderate quality "clock > > drive" on a scope, the tracking is not generally great and when you > > try to track for a minute or more errors (periodic and misalignment) > > in the clock drive will show up. So the fix these days is to piggyback > > a smaller scope onto the main scope and put a ccd camera on the "guide > > scope." The ccd camera is connected to a laptop via usb and the camera > > is read into the computer every few seconds. You select a star that > > the camera sees to use as a guide star and the computer tracks the > > errors in the measured star position when compared to the ideal and > > these errors are then Kalman filtered and the corrections are sent to > > the telescope's mount to keep the guide star centered up. > > > Another DSP aspect (a pretty simple one yet effective) is taking > > multiple short exposures (1 to 10 minutes each) and stacking them > > together to average out the noise. > > do you cross correlate each exposure to line it up before stacking?- Hide quoted text - > > - Show quoted text -I did this one manually, but I do have a program for aligning and rotating each image. It needs some improvement. Rotation of each image is needed if your telescope does not use a polar (equitorial mount). I do have such a mount so translation will suffice for me. For people using alt-azimuth mounts even if they keep a star in the field perfectly aligned from image to image, the field will rotate about that star. If you combined exposures add up to minutes or more this will become apparent. I'm working on an auto align program to speed up this process. It is not unusual for one to combine a hundred images! I'm still new at this so I haven't done one with more than 10 images yet. Clay
Reply by ●February 25, 20092009-02-25
On Feb 25, 12:05�pm, "bungalow_st...@yahoo.com" <bungalow_st...@yahoo.com> wrote:> On Feb 25, 10:54�am, c...@claysturner.com wrote: > > > > > > > Hello All, > > > In the world of astronomy we currently have comet Lulin which will be > > observable in binoculars and telescopes for another couple of months. > > So I set up my scope to take a picture of it. So the DSP part comes in > > two ways. > > > First since the Earth rotates you need to have your scope track the > > stars to counter the rotation. Even with a moderate quality "clock > > drive" on a scope, the tracking is not generally great and when you > > try to track for a minute or more errors (periodic and misalignment) > > in the clock drive will show up. So the fix these days is to piggyback > > a smaller scope onto the main scope and put a ccd camera on the "guide > > scope." The ccd camera is connected to a laptop via usb and the camera > > is read into the computer every few seconds. You select a star that > > the camera sees to use as a guide star and the computer tracks the > > errors in the measured star position when compared to the ideal and > > these errors are then Kalman filtered and the corrections are sent to > > the telescope's mount to keep the guide star centered up. > > > Another DSP aspect (a pretty simple one yet effective) is taking > > multiple short exposures (1 to 10 minutes each) and stacking them > > together to average out the noise. > > do you cross correlate each exposure to line it up before stacking?- Hide quoted text - > > - Show quoted text -I did this one manually, but I do have a program for aligning and rotating each image. It needs some improvement. Rotation of each image is needed if your telescope does not use a polar (equitorial mount). I do have such a mount so translation will suffice for me. For people using alt-azimuth mounts even if they keep a star in the field perfectly aligned from image to image, the field will rotate about that star. If you combined exposures add up to minutes or more this will become apparent. I'm working on an auto align program to speed up this process. It is not unusual for one to combine a hundred images! I'm still new at this so I haven't done one with more than 10 images yet. Clay
Reply by ●February 25, 20092009-02-25
On Feb 25, 12:05=A0pm, "bungalow_st...@yahoo.com" <bungalow_st...@yahoo.com> wrote:> On Feb 25, 10:54=A0am, c...@claysturner.com wrote: > > > > > > > Hello All, > > > In the world of astronomy we currently have comet Lulin which will be > > observable in binoculars and telescopes for another couple of months. > > So I set up my scope to take a picture of it. So the DSP part comes in > > two ways. > > > First since the Earth rotates you need to have your scope track the > > stars to counter the rotation. Even with a moderate quality "clock > > drive" on a scope, the tracking is not generally great and when you > > try to track for a minute or more errors (periodic and misalignment) > > in the clock drive will show up. So the fix these days is to piggyback > > a smaller scope onto the main scope and put a ccd camera on the "guide > > scope." The ccd camera is connected to a laptop via usb and the camera > > is read into the computer every few seconds. You select a star that > > the camera sees to use as a guide star and the computer tracks the > > errors in the measured star position when compared to the ideal and > > these errors are then Kalman filtered and the corrections are sent to > > the telescope's mount to keep the guide star centered up. > > > Another DSP aspect (a pretty simple one yet effective) is taking > > multiple short exposures (1 to 10 minutes each) and stacking them > > together to average out the noise. > > do you cross correlate each exposure to line it up before stacking?- Hide=quoted text -> > - Show quoted text -I did this one manually, but I do have a program for aligning and rotating each image. It needs some improvement. Rotation of each image is needed if your telescope does not use a polar (equitorial mount). I do have such a mount so translation will suffice for me. For people using alt-azimuth mounts even if they keep a star in the field perfectly aligned from image to image, the field will rotate about that star. If you combined exposures add up to minutes or more this will become apparent. I'm working on an auto align program to speed up this process. It is not unusual for one to combine a hundred images! I'm still new at this so I haven't done one with more than 10 images yet. Clay
Reply by ●February 25, 20092009-02-25
On Feb 25, 12:05=A0pm, "bungalow_st...@yahoo.com" <bungalow_st...@yahoo.com> wrote:> On Feb 25, 10:54=A0am, c...@claysturner.com wrote: > > > > > > > Hello All, > > > In the world of astronomy we currently have comet Lulin which will be > > observable in binoculars and telescopes for another couple of months. > > So I set up my scope to take a picture of it. So the DSP part comes in > > two ways. > > > First since the Earth rotates you need to have your scope track the > > stars to counter the rotation. Even with a moderate quality "clock > > drive" on a scope, the tracking is not generally great and when you > > try to track for a minute or more errors (periodic and misalignment) > > in the clock drive will show up. So the fix these days is to piggyback > > a smaller scope onto the main scope and put a ccd camera on the "guide > > scope." The ccd camera is connected to a laptop via usb and the camera > > is read into the computer every few seconds. You select a star that > > the camera sees to use as a guide star and the computer tracks the > > errors in the measured star position when compared to the ideal and > > these errors are then Kalman filtered and the corrections are sent to > > the telescope's mount to keep the guide star centered up. > > > Another DSP aspect (a pretty simple one yet effective) is taking > > multiple short exposures (1 to 10 minutes each) and stacking them > > together to average out the noise. > > do you cross correlate each exposure to line it up before stacking?- Hide=quoted text -> > - Show quoted text -I did this one manually, but I do have a program for aligning and rotating each image. It needs some improvement. Rotation of each image is needed if your telescope does not use a polar (equitorial mount). I do have such a mount so translation will suffice for me. For people using alt-azimuth mounts even if they keep a star in the field perfectly aligned from image to image, the field will rotate about that star. If you combined exposures add up to minutes or more this will become apparent. I'm working on an auto align program to speed up this process. It is not unusual for one to combine a hundred images! I'm still new at this so I haven't done one with more than 10 images yet. Clay
Reply by ●February 25, 20092009-02-25
On Feb 25, 12:05�pm, "bungalow_st...@yahoo.com" <bungalow_st...@yahoo.com> wrote:> On Feb 25, 10:54�am, c...@claysturner.com wrote: > > > > > > > Hello All, > > > In the world of astronomy we currently have comet Lulin which will be > > observable in binoculars and telescopes for another couple of months. > > So I set up my scope to take a picture of it. So the DSP part comes in > > two ways. > > > First since the Earth rotates you need to have your scope track the > > stars to counter the rotation. Even with a moderate quality "clock > > drive" on a scope, the tracking is not generally great and when you > > try to track for a minute or more errors (periodic and misalignment) > > in the clock drive will show up. So the fix these days is to piggyback > > a smaller scope onto the main scope and put a ccd camera on the "guide > > scope." The ccd camera is connected to a laptop via usb and the camera > > is read into the computer every few seconds. You select a star that > > the camera sees to use as a guide star and the computer tracks the > > errors in the measured star position when compared to the ideal and > > these errors are then Kalman filtered and the corrections are sent to > > the telescope's mount to keep the guide star centered up. > > > Another DSP aspect (a pretty simple one yet effective) is taking > > multiple short exposures (1 to 10 minutes each) and stacking them > > together to average out the noise. > > do you cross correlate each exposure to line it up before stacking?- Hide quoted text - > > - Show quoted text -I did this one manually, but I do have a program for aligning and rotating each image. It needs some improvement. Rotation of each image is needed if your telescope does not use a polar (equitorial mount). I do have such a mount so translation will suffice for me. For people using alt-azimuth mounts even if they keep a star in the field perfectly aligned from image to image, the field will rotate about that star. If you combined exposures add up to minutes or more this will become apparent. I'm working on an auto align program to speed up this process. It is not unusual for one to combine a hundred images! I'm still new at this so I haven't done one with more than 10 images yet. Clay
